Semiconductor devices typically include multiple individual components formed on or within a substrate. The way to prevent unwanted components or structures from cross talk or shorting becomes significantly important, since the integration circuit density is continuously increased. Therefore, isolation techniques are very critical for the purpose of electrically insulating various portions or structures of the semiconductor device from other portions of the device. A popular isolation technology used for sub-micron ultra-large scaled integrated (ULSI) technology is a technique known as “shallow trench isolation (STI)”.
Conventional trench processes includes etching a substrate surface to a depth, and then refilling the trench with a deposited dielectric layer. The dielectric layer is then planarized to complete the trench isolation structure. However, as the feature size shrinks and the aspect ratio of the trench increases, the gap filling ability becomes an important factor in selecting the filled dielectric material. Comparing to conventional deposition processes, spin-on glass processes have the advantage of excellent gap filling ability in filling trenches. Therefore, the spin-on glass becomes one of selected dielectric materials to fill the trench. Generally, the spin-on glass is formed by spin-coating a dielectric material over the substrate. Then, the coated dielectric material is annealed. The spin-on glass is then etched back to form a recess. A dielectric layer is subsequently deposited in the recess upon the spin-on glass. However, after the high temperature annealing process, the crack issue is likely to occur due to poor adhesion between the trench sidewall surfaces and the spin-on glass. The cracks between the spin-on glass and the trench sidewalls will reduce the isolation capability and a breakdown of the trench isolation may occur.
Therefore, there is a need to provide a trench isolation structure and a method of forming a trench isolation structure with enhanced adhesion between the filled dielectric layer and the trench sidewalls.